The Earth sings every day, with an electric chorus. With the right tuning, radios can eavesdrop on this sizzling symphony of crackles, pops and whistles - the melody of millions of lightning bolts. A listener in New Zealand can even hear a volcano in Alaska erupt, a new study reports.

Lightning strikes unleash intense bursts of visible light and very-low-frequency (VLF) radio waves, among other kinds of energy. With a VLF receiver, anyone can listen to the constant chatter of Earth's lightning, estimated at 8 million strikes every day. (Not every lightning bolt becomes a whistler.) A worldwide listening network is tuned to one particular lightning sound, called whistlers. These eerie electronic signals supposedly got their name from soldiers, who compared the sound to falling grenades. Modern ears might liken whistlers to a video game's "pew-pew-pew" soundtrack. [Listen to the Volcanic Whistling]

Whistlers are pulses of VLF radio energy that have traveled into space, leaping from one side of Earth to the other along the planet's magnetic field lines. Scientists monitor whistlers because the beautiful noise tells them about the planet's protective bubble of charged particles, called the plasmasphere. Whistlers on Venus and Jupiter suggest lightning also crackles on other planets.

Now, however, researchers have also linked a flurry of whistlers detected in Dunedin, New Zealand, to processes deep inside the Earth. For the first time, scientists have connected whistlers to volcanic lightning, according to a study published July 2 in the journal Geophysical Research Letters.